Something wrong with my tracking markers?
This seems your solve error is fine.
Did you set the scale? if not ...
Under Solve Panel
their si Orientation Panel
Scene orientation tools can be used for orienting object to bundles.
Floor
Use selected three markers to define a floor. Camera will be transformed in a way which makes the selected markers to be flat (have Z = 0).
Wall
Similar to the floor orientation, but defines a wall (selected tracks are placed onto OXZ plane).
Set Origin
Transform camera in a way which makes active track to be moved to a scene origin. Only translation is applied to the camera.
Set X, Y Axis
Transform camera in a way which makes active track to become on X or Y axis. No translation is applied, meaning scene origin which was specified before will be preserved.
Set Scale
Scale camera or tracking object in a way which makes distance between two selected tracks match the given value in Distance.
Apply Scale
Similar to Set Scale, but actually modifies the tracking data.
Distance
Distance in active scene units which is used by Set/Apply scale.
...  I hope this will fix the scale..